1. Field of the Invention
This invention relates generally to devices which skim the surface of a liquid, and, more particularly, to devices which skim the surface of a moving stream of liquid.
2. Prior Art
There are many different devices which are employed to skim the surface of a liquid for various reasons. Many chemical and food processes require surface skimming. Additionally, various requirements exist for the skimming of water surfaces. The surface of a moving stream or lake is often skimmed to remove floating matter such as oil, scum or various solid floating objects. Skimming is also required in various sewage treatment processes to remove floating matter which cannot be removed by other chemical or physical clarification methods in the overall sewage treatment process.
In oxidation ditch sewage clarification systems, intrachannel clarifiers are often employed. Examples of an intrachannel clarifier may be seen in applicant's U.S. Pat. Nos. 4,362,625; 4,383,922 and 4,457,844. Applicant's clarifier functions by utilizing the hydraulic head losses created by a moving stream of sewage as it passes around and under a stationary semi-submerged structure. Various methods have been used to remove floating matter from the clarified liquid leaving the clarifier. These include a series of baffles or mechanical skimming devices which move across the liquid surface. Baffles tend to disrupt and disturb the flow within the clarifier. Mechanical skimmers require frequent maintenance and consume energy, increasing system costs. One type of skimmer may be seen in applicant's U.S. Pat. No. 4,436,632, which utilizes a float controlled skimming device.